Interpretive Summary: Emerald ash borer (EAB) currently occurs in fifteen states in the United States, as well as Ontario and Quebec in Canada. A decline in ash tree strength following EAB infestation is potentially hazardous to public safety, particularly when trees are left standing for several years after dying. Hazards associated with dead or dying EAB-infected ash trees include arborist safety, along with users of community green spaces. Several cases exist of EAB-related ash tree failure occurring prematurely during the removal process. Thus, this study was conducted in 2009 to evaluate the strength of ash trees in northwest Ohio. Ash trees in three situations were examined, namely, ash trees that were visually un-infested, trees that were currently infested (within one to two years), and trees following EAB infestation (> two years) with dead canopies. Bending stresses were not affected by EAB infestations, but wood moisture was significantly lower in branches from trees with advanced EAB infestations. Significantly higher wood cracking was also documented. Wood in trees with advanced EAB infestation also had a significantly lower resistance to drilling compared to un-infested trees. These findings indicate EAD infestation could result in earlier than expected tree and branch failure.

Technical Abstract:
Emerald ash borer (EAB) currently occurs in fifteen states in the United States, as well as Ontario and Quebec in Canada. A decline in ash tree strength following EAB infestation is potentially hazardous to public safety, particularly when trees are left standing for several years after dying. Dead or dying EAB-infected ash trees pose a risk to arborist safety, along with users of community green spaces. Several cases exist of EAB-related ash tree failure occurring prematurely during the removal process. Thus, this study was conducted in 2009 to evaluate the strength of ash trees in northwest Ohio. Ash trees in three situations were examined, namely, ash trees that were visually un-infested, trees that are currently infested (within one to two years), and trees following EAB infestation (> two years) had dead canopies. Data from static loading tests indicated that bending stresses were not significantly lower in EAB infected trees, but examination of the fracture zone revealed that wood moisture was significantly lower in branches from trees with advanced EAB presence. Significantly higher wood cracking in the critical zone of failure was also documented. Wood in the basal areas of ash trees with advanced EAB infestation also had significantly lower resistance to drilling compared to wood in the basal areas of visually un-infested trees. The data does not quantify risk associated with EAB activity in ash trees, but presents important insights into the ways EAB activity may affect ash tree biomechanics. These findings indicate EAD infestation could result in earlier than expected tree and branch failure.